Wikipedia
Doodle is an Internet calendar tool for time management, and coordinating meetings. It is based in Zurich, Switzerland and has been operational since 2007.
Users are polled to determine the best time and date to meet. Meeting coordinators (administrators) receive e-mail alerts for votes and comments. Registration is required to have this function.
Doodle interacts with various external calendaring systems, such as IBM Lotus Notes. Through the use of a widget for Lotus Notes, users are able to create and manage Doodle polls within a Lotus Notes client application. Google Calendar, Yahoo Calendar, Microsoft Outlook and Apple iCal can be utilized with Doodle to track dates. Google Maps may also be used to share the location of the event.
Similar popular competing products, which may collectively be designated as "date matchers", include klavado, Dudle ( Free Software maintained by the TU Dresden, which is also offering a privacy enhanced version of Dudle), ScheduleOnce, Tungle (which ceased 3 December 2012), TimeBridge, WhenIsGood or Framadate.